Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method and apparatus for performing radio link monitoring and/or channel quality indicator measurement in a wireless communication system.
Related Art
Universal mobile telecommunications system (UMTS) is a 3rd generation (3G) asynchronous mobile communication system operating in wideband code division multiple access (WCDMA) based on European systems, global system for mobile communications (GSM) and general packet radio services (GPRS). A long-term evolution (LTE) of UMTS is under discussion by the 3rd generation partnership project (3GPP) that standardized UMTS.
In order to allow users to access various networks and services ubiquitously, an increasing number of user equipments (UEs) are equipped with multiple radio transceivers. For example, a UE may be equipped with LTE, Wi-Fi, Bluetooth (BT) transceivers, etc, for a wireless communication system, and global navigation satellite system (GNSS) receivers. For example, a UE may be equipped with a LTE module and a Bluetooth module in order to receive a voice over Internet (VoIP) service, multimedia service using a Bluetooth earphone. A UE may be equipped with a LTE module and a Wi-Fi module in order to distribute traffics. A UE may be equipped with a LTE module and a GNSS module in order to acquire location information additionally.
Due to extreme proximity of multiple radio transceivers within the same UE, the transmit power of one transmitter may be much higher than the received power level of another receiver. By means of filter technologies and sufficient frequency separation, the transmit signal may not result in significant interference. But for some coexistence scenarios, e.g. different radio technologies within the same UE operating on adjacent frequencies or sub-harmonic frequencies, the interference power coming from a transmitter of the collocated radio may be much higher than the actual received power level of the desired signal for a receiver. This situation causes in-device coexistence (IDC) interference. The challenge lies in avoiding or minimizing IDC interference between those collocated radio transceivers, as current state-of-the-art filter technology might not provide sufficient rejection for certain scenarios. Therefore, solving the interference problem by single generic radio frequency (RF) design may not always be possible and alternative methods needs to be considered.
Meanwhile, a UE may persistently perform measurement in order to maintain link quality with a serving cell. Specifically, the UE may persistently perform monitoring of link quality in order to determine whether communication with the serving cell is available or not. In 3GPP LTE, it is called radio link monitoring (RLM). If link quality of the serving cell is bad enough that communication with the serving cell is not available, the UE may declare a radio link failure. IF the UE declares the radio link failure, the UE may abandon maintaining communication with the serving cell, and may select a cell by a cell selection procedure. The UE may try to an RRC connection reestablishment with the selected cell.
Whether to reflect IDC interference for RLM and/or channel quality indicator (CQI) measurement is not defined yet. Accordingly, a method for performing RLM and/or CQI measurement considering IDC interference may be required.